BUG#34788 - malformed federated connection url is not handled

            correctly - crashes server !

Creating federated table with connect string containing empty
(zero-length) host name and port is evaluated as 0 (port is
incorrect, omitted or 0) crashes server.

This happens because federated calls strcmp() with NULL pointer.

Fixed by avoiding strcmp() call if hostname is set to NULL.

mysql-test/r/federated.result

@@ -2069,6 +2069,8 @@ a	b
 1	1
 DROP TABLE t1;
 DROP TABLE t1;
+CREATE TABLE t1 (a INT) ENGINE=federated CONNECTION='mysql://@:://';
+DROP TABLE t1;
 DROP TABLE IF EXISTS federated.t1;
 DROP DATABASE IF EXISTS federated;
 DROP TABLE IF EXISTS federated.t1;

mysql-test/t/federated.test

@@ -1738,4 +1738,11 @@ DROP TABLE t1;
 connection slave;
 DROP TABLE t1;
 
+#
+# BUG#34788 - malformed federated connection url is not handled correctly -
+#             crashes server !
+#
+CREATE TABLE t1 (a INT) ENGINE=federated CONNECTION='mysql://@:://';
+DROP TABLE t1;
+
 source include/federated_cleanup.inc;

sql/ha_federated.cc

@@ -643,12 +643,19 @@ static int parse_url(FEDERATED_SHARE *share, TABLE *table,
   if ((strchr(share->table_name, '/')))
     goto error;
 
+  /*
+    If hostname is omitted, we set it to NULL. According to
+    mysql_real_connect() manual:
+    The value of host may be either a hostname or an IP address.
+    If host is NULL or the string "localhost", a connection to the
+    local host is assumed.
+  */
   if (share->hostname[0] == '\0')
     share->hostname= NULL;
 
   if (!share->port)
   {
-    if (strcmp(share->hostname, my_localhost) == 0)
+    if (!share->hostname || strcmp(share->hostname, my_localhost) == 0)
       share->socket= my_strdup(MYSQL_UNIX_ADDR, MYF(0));
     else
       share->port= MYSQL_PORT;